Water & Wastewater Treatment

www.wwtonline.co.uk | WWT | november 2014 | 17 The 4,000 square metre constructed wetland represents the first time aera- tion technology has been used on this scale in Scotland A constructed wetland scheme at Cowdenbeath Wastewater Treatment Works has allowed Scottish Water to treat discharges from combined sewer overflows (CSOs) in a way which meets regulatory demands and enhances the local environment. The £8.7 million project involved the construction of two units: a flow balancing sha- settlement system for sedimentation of solids and a 4,000 square metre, two metre deep saturated, vertical flow aerated wetland fitted with Forced Bed Aeration (FBA). It is the first time an aerated reed bed has been used on this scale in Scotland. Located to the south of Cowdenbeath Golf Course, the WWTW receives wastewater from CSOs serving 11,000 people in Cowdenbeath, which was previously stored and pumped to larger works for treatment. Scottish Water decided to upgrade the facility in 2011 a-er the Scottish Environment Protection Agency (SEPA) identified that the nearby Lochgelly Burn was being polluted during heavy storm events. "The initial driver for the project was that our regulator, SEPA, identified water quality and aesthetic failings relating to burns in that area that they believed were being caused by sewage discharges from Scottish Water assets," says Eddie Burns, project manager at Scottish Water. "The asset in this case pumps Wastewater treatment Aerated reed beds tackle CSO discharges at Cowdenbeath flow to another works, and what was happening was that anything above a certain pump volume would discharge. There was some storage at this facility but when it went above a certain level - in heavy storm conditions - the rest was discharged to the local watercourses." Scottish Water engaged engineering consultancy Atkins to investigate possible solutions: one option was the installation of a large new pipeline to the closest works in Lochgelly. However, an on-site natural treatment system, consisting of a tank and a constructed wetland, was favoured. "The wetland was preferred because it could be put in close to our existing assets and close to the watercourse, meaning a reduced impact on the environment and a Project focus ● £8.7M project treated sewage overflows and enhanced environment ● Segmented storage tank designed to be cleaned from above ● Automated pumping and aeration system requires minimal operator intervention James Brockett ediTor, WATer & WASTeWATer TreATmenT ● the need to meet sePa limits of 9.0 mg/l BoD and ammonia-nitrogen limits of 1.5 mg/l ● an additional treatment solution was needed close to existing scottish Water assets ● storage facilities need- ed to cope with irregular flow due to varied weather conditions • Drivers • Innovations ● aeration technology allowed 2m deep reed bed, enhancing treat- ment ● segmented storage tank designed to be cleaned from above ● automated pumping and aeration system re- quires minimal operator intervention

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